Colorado Rockies’ Nolan Arenado stands in the dugout with a splint on his finger during a baseball game against the Atlanta Braves, Saturday, May 24, 2014, in Atlanta. The Rockies placed Arenado on the 15-day disabled list Saturday, one day after he broke his left middle finger on a head-first slide into second base.

MILWAUKEE — Reinforcements are on the way, but the grind of baseball’s 162-game season continues to take its toll on the Rockies.

Friday, the Rockies announced that Gold Glove third baseman Nolan Arenado and left-handed starting pitcher Brett Anderson will start their Triple-A rehab work next week.

In the meantime, catcher Wilin Rosario, struggling through a disappointing season, was not in the starting lineup Friday against the Brewers at Miller Park because of lingering tightness in his lower back. Rosario is listed by the Rockies as day to day.

Arenado will make his first rehab start with Colorado Springs on Sunday. If the broken middle finger of his left hand checks out after a few Triple-A games, he could be back in the Rockies’ lineup in time for their next homestand, which begins Thursday against the Los Angeles Dodgers. Arenado broke the finger May 23 and went on the disabled list the next day. Colo- rado entered Friday’s game 9-22 without Arenado in the lineup.

Anderson, out since April 13 because of a fractured left index finger suffered during an at-bat, threw an impressive bullpen session Friday at Miller Park. He is scheduled to throw another bullpen session Sunday in Milwaukee, then make his first rehab start Wednesday with the Sky Sox. He needs to build up arm strength, so there is no exact timetable for his return to the Rockies’ rotation.

Footnotes. Right-hander Tyler Chatwood (strained elbow) is in Denver getting treatment. “It’s not a setback, but we are being cautious because it’s an elbow,” Weiss said. … Veteran reliever Rafael Betancourt, making a comeback from Tommy John surgery, threw a 20-pitch bull- pen session with the Rockies’ rookie-level team in Grand Junction on Friday.